GEOLOGY PROJECT

TOPIC- CLASSIFICATION OF SEDIMENTARY ROCKS

GROUP MEMBERS

1.AYUSH KUMAR (ROLL019)

2.SHAKTI SHEKHAR (ROLL067)

3. SHASHI KUMAR SRIVASTAV (ROLL069)

Sedimentary rocks• Sedimentary rocks are types of rock  that

are formed by the  deposition of material at the Earth's surface and within bodies of water. 

Or• Sedimentary rocks are formed by the

lithification of inorganic and/or organic sediments, or as chemical precipitates.

CLASSIFICATION OF SEDIMENTARY ROCKS

There are two types of sedimentary rocks:

1. Clastic 2. Chemical

Clastic sedimentary rocks

• Clastic sedimentary rocks form when existing parent rock material is weathered, fragmented, transported, and deposited in layers that compact, cement, and lithify to form sedimentary rocks.

Chemical sedimentary rocks

Chemical sedimentary rocks are formed by a variety of processes and are divided into sub-categories including inorganic, and biochemical or organic chemical sedimentary rocks.

Clastic sedimentary rocks

• Few examples of clastic sedimentary rocks are Limestone Breccia Chert Sandstone Shale Mudstone Conglomerate

Chemical sedimentary rocks

Few examples of chemical sedimentary rocks areFlintChertJasperDolomiteMagnesiteRock saltGypsum

Relative Percentages of Sedimentary Rocks

Sedimentary Rocks in North America

Classification of Clastic sedimentary rocks

S.NO TYPE GRAIN SIZE ROCK

1. GRAVELS Boulders >256mm Conglomerate

Cobbles 16-256mm

Pebbles 2-16mm

2. SANDS Coarse ½ -2 mm Quartz sandstone

Medium ¼ - ½ mm

Fine 1/16 – ¼ mm

3. SILTS 1/256-1/16 mm Shale, Siltstone

4. CLAYS < 1/256mm Mudstone

CLASSIFICATION OF CHEMICAL SEDIMENTARY ROCKS

S.NO TYPE SUB-TYPE CHARACTERISTICS1. CHEMICALLY

FORMED ROCKSSiliceous(Flint, chert, jasper)

Silica is chief constituent

Carbonate(Dolomite , magnesite)

Precipitated from carbonate rich waters

Ferruginous Oxides and hydroxides are common examples

Phosphatic Form from sea water rich in phosphoric acid

Evaporites(Rock salt, gypsum)

Formed from evaporation

S.NO TYPE SUB-TYPE CHARACTERISTICS

2. ORGANIC DEPOITS

Carbonate Formed by gradual accumulation of shells and skeletal bones of sea organism

Carbonaceous(Coal)

They are rich in carbon its main source is plants

Phosphatic Deposits-Guano

Accumulation of excreta of some birds

FerruginousDeposits

Mostly iron carbonate deposits , from fresh water lakes

DIFFERENT SEDIMENTARY ROCKS

Chert

• Chert is composed of silicon dioxide (SiO2). • It occurs as nodules, concretionary masses

and as layered deposits.• Chert is a very hard material that produces a

spark when it is struck against steel. The heat from this spark can be used to start fires

Limestone

• Limestone is a sedimentary rock composed primarily of calcium carbonate (CaCO3) in the form of the mineral calcite.

• It most commonly forms in clear, warm,shallow marine waters.

• Limestone can also form through evaporation. Stalactites, stalagmites and other cave formations (often called "speleothems") are examples of limestone that formed through evaporation.

Breccia

• Breccia are composed of large angular fragments (over two millimeters in diameter). The spaces between the large angular fragments can be filled with a matrix of smaller particles or a mineral cement that binds the rock together.

• Breccia forms where broken,angular fragments of rock or mineral debris accumulate.

• Possible location for breccia formationis at the base of an outcrop where mechanical weathering debris accumulates or alluvial fan. Some breccias form as debris flow deposits.

Conglomerate

• Conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together.

• Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts. Both conglomerates and breccias are characterized by clasts larger than sand (>2 mm)